Move pointerevent.js to src/

[jzaefferer]

I see no reason for this one file to be in the root directory. Moving it would simplify the build a bit, only need to list src/ in Gruntfile.js and package.json.

Or is there a reason to keep it as is?

[scottgonzalez]

This is just how the repo was organized when we adopted it. I'm fine with changing this.